Masonry block having a cavity web

ABSTRACT

A cementitious composite and cured masonry block made from the cementitious composite. The cementitious composite contains a cement, a non-rubber aggregate, a crumb rubber and at least one of cement kiln dust and limestone powder. The crumb rubber aggregate is extracted from scrap tires after being processed and then mixed in specified percentages with the aggregate, the cement and water, then cured in forms to make the masonry blocks. In the present disclosure sand, which is used in conventional masonry blocks, is at least partially replaced with crumb rubber to produce a sand-free or sand-reduced masonry block that contains crumb rubber. The crumb rubber masonry blocks satisfy the ASTM non-load bearing requirements. The use of crumb rubber decreases the unit weight and increases thermal resistance of the masonry blocks. The use of cement kiln dust or limestone as a partial replacement of cement will lead to decrease in the cost. The use of industrial waste materials, such as crumb rubber, limestone powder and cement kiln dust, will lead to economic and environmental benefits.

BACKGROUND OF THE INVENTION Technical Field

The present invention relates to composite compositions containing acement, crumb-rubber particles, one or more aggregates, and at least oneof limestone powder and cement kiln dust. The present disclosure furtherrelates to masonry blocks made from the cured composite compositions.

Description of the Related Art

The “background” description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent it is described in thisbackground section, as well as aspects of the description which may nototherwise qualify as prior art at the time of filing, are neitherexpressly or impliedly admitted as prior art against the presentinvention.

Innovative, environmentally friendly and ready-to-use buildingcomposites (e.g., composite compositions) that provide a combination ofhigh efficiency, quality and improved thermal resistance have long beensought. This search has been ongoing in an environment with increaseddemand on both thermal and mechanical (thermo-mechanical) performance ofnew building products integrated with various plasters, foils, particlesand rubbers.

The demand for new low-cost and efficient building materials hasincreased together with an increase in population, leading to a chronicshortage of easily accessible (affordable) building materials. Engineershave attempted to address these shortages by utilizing industrialby-products in the formulation and production of useful buildingmaterials. Repurposing materials previously viewed as waste addressesproblems related to the accumulation of waste materials in areasundergoing rapid population growth. This has become a significantenvironmental concern, especially in developing countries. Recyclingindustrial by-products and wastes for use as building materials is aviable solution not only to environmental problems but also it providesa means to substantially lower the construction costs of new buildingsand shelters.

The increase in the popularity of using environmentally friendly, lowcost and lightweight construction materials in the building industrybrings the need for searching more innovative, flexible and versatilecomposites for a variety of applications. The most important aspects ofinnovation might be in the development of integrated insulationproducts, such as the insulated, reinforced concretes, two or three-wayprecast sandwich wall panels, and rubberized concretes. Part of thisinterest is to establish the thermal performance of the alternativesystems and products. Excellent thermal characteristics are required toguide product development and manufacturing. Methods and data exist fordealing with the common building walls and insulations, but new systemsand products are generally lacking such supporting data and expertise.

The public has a physiological barrier to the use of products that aremade of crumb rubber (or waste tires). This has hindered the utilizationof crumb rubber (CR) in important applications, such as flooring andplaygrounds. The present disclosure describes CR-containing constructionproducts and applications that are not in direct contact with people.This will increase the public's acceptance of CR-containing materials.

Scrap tires, which are ordinarily treated as waste, can instead beconsidered as useful material as a source of CR. CR is a valuableproduct with ongoing expansion and growth in diversified markets. It isfar better to remove tires from the waste stream, regardless of disposalmethod, than to allow the continued uncontrollable destruction of thisresource in fires throughout the world. The materials extracted fromscrap tires can be used in the CR supply chain. The CR-containingmasonry blocks described herein are able to meet ASTM standards adoptedfor the utilization of masonry blocks in non-loading applications.Recycling CR has the potential of a tremendous positive environmentalimpact since scrap tires are conventionally burned due to the lack ofotherwise suitable applications.

Cementitious composites containing scrap tire rubber (e.g., anindustrial by-product or waste) offer significant advantages incomparison to the conventional cementitious composites. The inclusion ofCR in cement-based concrete mixtures may lead to significant benefits,such as lower density, increased toughness and ductility, higher impactresistance, and more efficient heat and sound insulation. The use ofrecycled tire rubber (e.g., CR) in cementitious products may also helpto alleviate disposal problems related to used tires and it also addressthe growing public concerns regarding the consumption of natural sandsand aggregates.

Accordingly, it is one objective of the present disclosure to describecementitious CR-containing composites for use in construction and foruse in the formation of cured masonry products.

BRIEF SUMMARY OF THE INVENTION

The foregoing paragraphs have been provided by way of generalintroduction, and are not intended to limit the scope of the followingclaims. The described embodiments, together with further advantages,will be best understood by reference to the following detaileddescription taken in conjunction with the accompanying drawings.

According to a first aspect, the present disclosure relates to acementitious composite containing i) a cement, ii) a first aggregate,which is not crumb rubber, iii) crumb rubber and (iv) cement kiln dustor limestone powder.

According to another aspect, the present disclosure relates to a masonryblock made from a cured cementitious composite containing i) a cement,ii) a first aggregate, which is not crumb rubber, iii) crumb rubber and(iv) cement kiln dust or limestone powder

In one embodiment, the crumb rubber is in the form of coarse particleshaving a particle size of 1.5-5 mm, fine particles having a particlesize of 50-250 μm, or a mixture of the coarse and fine particles.

In one embodiment, the crumb rubber is in the form of coarse particleshaving a particle size of 2-3 mm.

In one embodiment, the crumb rubber contains fine particles having aparticle size of 50-250 μm.

In one embodiment, the fine particles have a particle size of 100-150μm.

In one embodiment, a ratio of the coarse particles to the fine particlesis from 2:1 to 1:2.

In one embodiment the cementitious composite contains cement kiln dustor limestone powder.

In one embodiment, the invention includes a cured composite having aunit weight of 1000-1,250 kg/m.

In one embodiment, the cured composite is in the form of a masonry blockhaving a water absorption of 6.0-9.0% as determined by ASTM C 642.

In one embodiment, an aggregate present in the cementitious composite isa crushed recycled concrete material.

In one embodiment, no aggregate, filler, or additive which comprises agroup 13 element is present in the cementitious composite. In oneembodiment, the group 13 element is boron.

In one embodiment, the crumb rubber is silanized crumb rubber obtainedby treating crumb rubber with a silanizing agent selected from the groupconsisting of an aminosilane, a glycidoxysilane, and a mercaptosilane.In one embodiment, the aminosilane is selected from the group consistingof (3-aminopropyl)-diethoxy-methylsilane,(3-aminopropyl)-dimethyl-ethoxysilane, and(3-aminopropyl)-trimethoxysilane. In one embodiment, the glycidosilaneis (3-glycidoxypropyl)-dimethyl-ethoxysilane. In one embodiment, themercaptosilane is (3-mercaptopropyl)-trimethoxysilane or(3-mercaptopropyl)-methyl-dimethoxysilane.

In one embodiment, the crumb rubber is carboxylic acid surface modifiedcrumb rubber obtained by treating crumb rubber with hydrogen peroxide.

In one embodiment, the cured cementitious composite has a wt % of crumbrubber ranging from 12 to 18%, relative to the total weight of the curedcementitious composite.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the disclosure and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 shows a conventional masonry block;

FIG. 2 shows a masonry block made from a cured cementitious compositecontaining crumb-rubber.

FIG. 3 shows features of a masonry block.

FIG. 4A shows a solid masonry block or brick.

FIG. 4B shows a solid masonry block having a textured and scoredsurface.

FIG. 5A shows a rectangular masonry block with two cavities.

FIG. 5B shows a rectangular masonry block with two cavities and a scoredend face.

FIG. 5C shows a low height rectangular masonry block with two cavities.

FIG. 5D shows a narrow rectangular masonry block.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present disclosure will now be described more fullyhereinafter with reference to the accompanying drawings, in which some,but not all embodiments of the disclosure are shown.

Any type of cement or cement containing material may be used in any ofthe embodiments disclosed herein. For example, cement may include TypeI, Type la, Type II, Type IIa, Type III, Type IIIa, Type IV and Type VPortland cements (using either the ASTM CI50 standard or the EuropeanEN-197 standard), hydraulic cements, non-hydraulic cements, Portland flyash cement, Portland pozzolan cement, Portland silica fume cement,masonry cements, mortars, EMC cements, stuccos, plastic cements,expansive cements, white blended cements, pozzolan-lime cements,slag-lime cements, supersulfated cements, calcium aluminate cements,calcium sulfoaluminate cements, geopolymer cements, Rosendale cements,polymer cements, lime mortar, and/or pozzolana mortar.

In one embodiment SiO₂ may be present in cement. Cement may includeSiO₂-containing materials including but not limited to belite(2CaO.SiO₂), alite (3CaO.SiO₂), celite (3CaO.Al₂O₃), or brownmillerite(4CaO.Al₂O₃.Fe₂O₃). Sand may be present in an amount of up to 50 wt %,preferably up to 40 wt %, preferably up to 30 wt %, preferably up to 20wt %, preferably up to 15 wt %, preferably up to 10 wt %, preferably upto 5 wt %, with a minimum amount of 0.5 wt %, preferably 1 wt %.

In one embodiment the masonry blocks are made by mixing cement withcrumb rubber in the at least partial absence of sand, with water. Thewater-containing composition is then cured such that at least a portionof the water is chemically reacted with the cement during curing. Inanother embodiment the masonry blocks are made with cement-containingsand and that is mixed with crumb rubber. Preferably, a minimum amountof sand, based on the total amount of the sand and the crumb rubber, (orno sand) is present as an aggregate component in the cementitiouscomposite or the cured masonry block.

In the present disclosure, sand is at least partially replaced withcrumb rubber,and cement is at least partially replaced with cement kilndust and/or limestone powder to form a cementitious composite useful forforming masonry blocks comprising cement, a non-rubber aggregate, and atleast one of cement kiln dust and limestone powder (which may be inreacted form after curing), and crumb rubber. In one embodiment, themasonry block consists of the cured cement, the non-rubber aggregate,the crumb rubber and at least one of reacted or non-reacted cement kilndust and limestone powder.

Cement kiln dust (CKD) is a by-product of cement production. Dust isgenerated during the combustion of gases during the production of cementin a kiln. The heated gases rapidly escape the kiln and carry entrainedparticulate matter that is typically captured by air pollution controlequipment and collected for disposal. CKD is often disposed as a waste.Today, only a relatively small quantity of CKD produced in the world isrecycled or utilized in a useful manner.

CKD is a fine dry powder with alkaline characteristics. Ordinarily CKDmust be protected from the atmosphere or else it will quickly absorbwater and form semi-cured coarse aggregates. CKD can have differentparticulate characteristics depending on the type of kiln in which it isgenerated and/or the fuels or other raw materials present during theprocess for making cement. Cement kiln dust can be obtained from wet ordry kiln processes with differing particle size, composition and pHcharacteristics.

The CKD present in the cementitious composition of the presentdisclosure is preferably obtained from a dry kiln process. Particle sizecharacteristics may vary in a range of 0.1-100 μm. Preferably. at least90 wt %, preferably 90 wt %, 95 wt % or 99 wt % of the CKD in thecementitious composite has a particle size within this range. In apreferred embodiment of the invention the CKD has an average particlediameter of 5-50 μm, preferably 10-35 μm, 15-30 μm or about 10-20 μm.The quantity of CKD particles with a particle diameter of more than 50μm is preferably no more than 30 wt %, preferably no more than 20 wt %,preferably not more than 10 wt %, preferably not more than 5 wt % basedon the total weight of the CKD. Generally the CKD, when dry andimmediately after collection, will completely pass through a screen sizeof 10 mesh or 20 mesh; generally at least 80% of CKD will pass through ascreen size of 50 mesh; and at least 70% by weight will pass through ascreen size of 200 mesh.

CKD has conventionally been used as a barrier to water transport, suchas landfill liners or other applications in which a water/soil barrieris desirable. This property of low hydraulic conductivity may, undersome circumstances, be unfavorable for the utilization of CKD as aneffective component of a cementitious composition. Low hydraulicconductivity may negatively affect quick dispersion and flow propertiesof concrete compositions obtained by mixing CKD-containing cementcompositions with water prior to curing, for example prior to flowinginto a mold to form a formed article, such as a masonry block. In orderto improve the hydraulic conductivity and dispersibility, and likewiseimprove cure time, CKD may be treated chemically prior to inclusion inthe cementitious composition of the present claims. In one embodimentthe CKD is mixed with glass fibers at elevated temperatures, e.g.,temperatures of from 300-1,200° C., preferably a temperature that is atleast 100° C., preferably 150 or 250° C. lower than the melting point ofthe glass fiber with which the CKD is mixed. Mixing CKD with glass fiberat high temperature permits micro-bonding, both chemical and physical,to occur between individual CKD particles and individual glass fibers.Physical connections may arise by simple diffusion or semi-melt contactbetween a CKD particle and a glass fiber. CKD particles can chemicallyreact with glass fibers when a portion of the silicate structure of theglass fiber diffuses into and/or interacts with the chemical compositionof the cement kiln dust whereby the CKD particle exchanges molecularstructure positions with portions of the glass fiber. The combinedCKD/glass fiber particle provides synergistic advantages such that bothimproved mixing and dispersion of the CKD particle in a concretecomposition is obtained and the benefits of improved strength from glassfibers is also realized. In this manner, the CKD has improved hydraulicconductivity in comparison to the hydraulic conductivity of CKD that isotherwise not reacted with or treated with glass fibers at hightemperature. Hydraulic conductivities as great as 5×10.2 cm/sec,preferably ±10%, ±25% or ±50% may be obtained for compacted CKD/glassfiber treated particulate material (where ±means±10%, preferably 5%).

In a still further embodiment of the invention either the CKD orpreferably the glass fibers may be contacted with an etching agent suchas hydrogen fluoride. The etching agent makes co-substitution ofchemical matrices between the CKD and the glass fiber more likely andfacile, and thus occurs at lower temperatures. In one embodiment of theinvention, a CKD is first contacted with a hydrogen fluoride(HF)-containing composition or HF gas to chemically etch the CKDparticles and, for example, form a CKD particle that is deficient insilicon dioxide and preferably forms a CKD that has been enriched withsilicon fluorides. Therefore, in a preferable embodiment of theinvention the CKD contains fluoride ions (F—) in an amount of from0.005-0.1 wt %, preferably 0.01-0.05 wt %.

The glass fibers are preferably alkali resistant (AR) glass fibers thatmay be present in an amount of, for example, 0.5-5% by weight,preferably 1-4% or 2-3% by weight. The glass fibers are typically ofsmall size, smaller than that used in conventional glass fiberreinforced concrete (GFRC). For example, the glass fibers are in theform of individual filaments having a diameter of from 5-50 μm,preferably 10-40 or 20-30 μm. Fiber length may vary from at least 2times fiber diameter up to 5 mm, preferably up to 4 mm, 3 mm, 2 mm, 1mm, or 0.5 mm.

The chemical composition of CKD may vary depending upon the conditionsof cement manufacture. Nonetheless, the CKD particles used in thecementitious composition of the present disclosure preferably contain amixture of silicates, calcium oxide, carbonates, potassium oxide,sulfates, chlorides, and metal oxides, such as sodium oxide. Chemicalcomponents of CKD are tabulated below.

Compound Composition SiO₂ 2.0-20 wt %, preferably 4.0-15 wt %,preferably 6.0-12 wt %, preferably 8-10 wt % Al₂O₃ 0.1-5 wt %,preferably 0.5-4 wt %, preferably 1-3 wt %, preferably about 2.5 wt %TiO₂ 0.01-2 wt %, preferably 0.05-1 wt % Fe₂O₃ 0.1-5 wt %, preferably0.5-2.5 wt %, preferably 1-1.5 wt % Mn₂O₃ 0.01-0.1 wt %, preferably0.03-0.01 wt % CaO 5-60 wt %, preferably 8-55 wt %, preferably 10-50 wt%, preferably 12-45 wt %, preferably 15-40 wt %, preferably 20-30 wt %MgO 0.1-5 wt %, preferably 0.5-2.5 wt %, preferably 1.0-1.5 wt % K₂O0.1-10 wt %, preferably 0.5-8 wt %, preferably 1-5 wt %, preferably 2-4wt % Na₂O 0.05-2.5 wt %, preferably 0.1-2 wt %, preferably 0.5-1.5 wt %

CKD is typically alkaline having a pH measured under leachate testingconditions of 8-13.5, preferably 10-12, preferably about 11. A varietyof metal oxides, including transition metal oxides, may be present inminor quantities (for example 1% by weight or less), in the CKD. Ironoxide is preferable component of the CKD and may be present in amountsof greater than 1%, e.g., in an amount of as much as 10 wt %. Fe₂O₃ mayaffect the curing times and resultant compressive strength of the curedcementitious composition. Greater amounts of iron oxide decrease time togain strength by as much as 30%, as much as 20%, or as much as 10% incomparison to cementitious compositions that contain no iron oxide or anamount of iron oxide that is less than 0.5 wt %.

In a preferred embodiment of the invention, the cementitious compositioncontains limestone powder (LSP). The limestone powder is preferablyobtained as a waste or by-product from quarrying in naturally occurringlimestone formations. The limestone powder may be of irregular shape andparticle size, such as the limestone powder obtained by cuttingnaturally occurring limestone with a rock saw. Limestone is asedimentary rock that is principally composed of the minerals calciteand aragonite. Each of these minerals is a form of calcium carbonate(CaCO₃). Calcium carbonate exists naturally in formations throughout theworld. It is sometimes used as a component of cement but in the presentdisclosure the limestone powder content is calculated independently ofany limestone aggregate already present in the cement component. It ispreferably used without further purification or chemical modification orcrushing to form a powder. However, in some embodiments the limestonemay be chemically or physically treated in order to modify or enhanceits chemical or physical properties. For example, the limestone powdermay be heated at temperatures sufficient to at least partially convertthe calcium carbonate to calcium oxide and/or calcium hydroxide. Thelimestone powder may be subject to thermal treatment in the presence ofcement and/or a zeolite which may function to exchange calcium foralumina within the mineral structure.

In other embodiments of the invention, the limestone powder is treatedphysically to alter the particle size of the limestone powder. Limestonepowder generated by quarrying operations may be dependent on manyfactors such as low conditions, e.g., the density and purity of thenaturally-occurring limestone deposit, weather conditions duringquarrying and the conditions of equipment and the operating parametersunder which it is used. The sharpness and/or freshness of a rock sawused to quarry limestone, and the speed at which it is advanced througha limestone deposit, may have dramatic effects upon the particle size ofthe limestone powder obtained by quarrying using the rock saw. In oneembodiment the limestone powder is subject to separate crushing orpulverizing to form a limestone powder of more uniform particle size orparticle size distribution. In a still further embodiment the limestonepowder may be classified by size prior to its inclusion in thecementitious compositions of the present disclosure. Size classificationmay be carried out using a series of sieves of gradually tighter meshsize. The limestone powder preferably has an average particle size offrom 1 to 50 μm, preferably 2-40 μm, 3-35 μm, 4-30 μm, 5-25 μm, 6-20 μm,8-18 μm, 10-15 μm or about 12 μm. The specific gravity of the limestoneparticles generally range from about 2.4 to about 2.8, preferably2.5-2.6 or about 2.7. In other embodiments of the invention, one or moreaggregates present in the cementitious composition may be a limestoneaggregate having a substantially greater particle size than thelimestone powder. For example, the aggregate may be a crushed limestonehaving an average particle size of 500 μm or greater, preferably greaterthan 1 millimeter, preferably greater than 5 millimeter, preferablygreater than 10 millimeter or preferably greater than 100 millimeter.

The limestone powder is preferably present in the cementitiouscomposition in a minor amount. For example, the limestone powder may bepresent in an amount that is less than the total amount of the cement.In some embodiments, the limestone powder is present in an amount thatis equal to the amount of cement, preferably no greater than 10% amountgreater than the total amount of cement in the cementitious composition.In one embodiment of the invention, limestone powder is in the range of25 to 50% of the cementitious composition. In another embodiment of theinvention, CKD constitutes 35 to 45% of the cementitious composition.

The crumb rubber present in the cementitious powder is preferablypresent as a mixture of coarse and fine mesh particles. In a preferableembodiment of the invention there are at least three distinct particletypes of crumb rubber in the cementitious composition, a first coarsemesh size of 1-5 mm, a second coarse mesh size of 0.5-1 mm and a finemesh size of 100-200 μm. The first coarse mesh size is preferably 2-4 mmor 2-3 mm and the second coarse mesh size is preferably 0.6-0.9 mm or0.7-0.8 mm. The fine mesh size is preferably 125-175 μm or about 150 μm.The first and second coarse mesh size crumb rubber particles are presentin a weight ratio of 1:1. The total amount of first and second coarsemesh crumb rubber particles are present in a weight ratio with respectto the total weight of the fine coarse mesh crumb rubber particles of4:1.

Crumb rubber is usually obtained from recycled tires that are ground toabout the size of a lump of coal. Thereafter the coal-size particles areground down to about the size of a walnut, with further grindingtechniques bringing the walnut size pieces of rubber down to a lowermesh size. The crumb rubber may be in the form of coarse particleshaving a particle size of 1.5-5 mm, fine particles having a particlesize of 50-250 μm, or a mixture of the coarse particles and the fineparticles.

In one embodiment, the crumb rubber is in the form of coarse particleshaving a particle size of 1.5-5 mm, or 1.6-4.5 mm, or 1.7-4 mm, or1.8-3.5 mm, or 1.9-3.2 mm, or 2-3 mm.

In one embodiment, the crumb rubber is in the form of fine particleshaving a particle size of 50-250 μm, or 60-240 μm, or 70-230 μm, or80-220 μm, or 90-210 μm, or 100-200 μm, or 100-180 μm, or 100-160 μm, or100-150 μm, or 100-148 m or, 100-140 μm. Preferably, the fine particlesof crumb rubber have a mesh size of 65-100 mesh, 70-100 mesh, 75-95mesh, 80-90 mesh, or an 80 mesh (177 μm) size.

In one embodiment, the cementitious composition contains a mixture ofthe coarse particles and fine particles. A ratio of the coarse particlesto the fine particles (by weight) may range from 2:1 to 1:2, or 1.9:1 to1:1.9, or 1.8:1 to 1:1.8, or 1.7:1 to 1:1.7, or 1.6:1 to 1:1.6, or 1.5:1to 1:1.5, or 1.4:1 to 1:1.4, or 1.3:1 to 1:1.3, or 1.2:1 to 1:1.2, or1.1:1 to 1:1.1, or about 1:1.

In one embodiment, the crumb rubber particles of the present disclosureare treated with a surface treatment agent, such as hydrogen peroxide,to form treated particles having more carboxylic sites than untreatedparticles. The functional groups in the mixture containing water,aggregate, and cement then interact with the carboxylic sites, therebycausing the treated crumb rubber particles to contact with and besuspended in the mixture to a much greater degree than untreatedparticles.

Preferably, the crumb rubber particles are as small as possible so thatthey are most easily suspended in the mixture. The particles can betreated by mixing them with hydrogen peroxide at a temperature of about65-85° C. while stirring for about 20 to 30 minutes to produce afreely-flowing powder. Preferably, the amount of hydrogen peroxide usedis 0.035-0.040 milli-moles of peroxide per gram of mixture.

In another embodiment of the disclosure, the crumb rubber may also becompressed at high pressure in the presence of a specialized urethane,sodium silicate or any other acceptable glues. Preferably, the crumbrubber is compressed at a high pressure in the presence of a sodiumsilicate. In one embodiment, the applied pressure is stepped until thecrumb rubber is flowable by first applying 1600 psi and then in 15second intervals stepping up the pressure by 500 psi until the pressurereaches to 3600 psi.

In another embodiment, the crumb rubber can be treated with a silanizingagent including but not limited to aminosilanes, glycidoxysilanes, andmercaptosilanes. Such aminosilanes include but are not limited to(3-aminopropyl)-diethoxy-methylsilane,(3-aminopropyl)-dimethyl-ethoxysilane, and(3-aminopropyl)-trimethoxysilane. Such glycidoxysilanes include but arenot limited to (3-glycidoxypropyl)-dimethyl-ethoxysilane. Suchmercaptosilanes include but are not limited to(3-mercaptopropyl)-trimethoxysilane and(3-mercaptopropyl)-methyl-dimethoxysilane. The organo-functionalalkoxysilane group of the silanizing agent interacts with the hydroxylgroups of the crumb rubber to displace the alkoxy groups attached to thesilane molecule and a crumb rubber matrix containing the silanized crumbrubber is formed.

In a preferred embodiment of the invention, the organic content of thecementitious composition (e.g., the content of materials that containcarbon to carbon (C—C) bonds) is derived mainly from the crumb rubber.For example, it is preferable that the only organic content is fromcarbonaceous materials present in the crumb rubber. In otherembodiments, the cementitious composition and/or a cured derivative ofthe cementitious composition may contain organic compounds of which atleast 95% by weight, preferably at least 98% by weight, 99% by weight,99.5% by weight or 99.9% by weight are derived from the crumb rubberwhere weight percent is based upon the total weight of all of thecarbonaceous organic materials present in the cementitious compositionand/or cured derivative thereof. Small quantities of additives, such ascuring agents or flow modifiers, may be present such that some organiccontent is present from sources other than the crumb rubber.

Exemplary aggregates include: crushed recycled concrete, gravel, rocks,natural soil, quarried crushed mineral aggregates from igneous,metamorphic or sedimentary rocks, including unused and waste aggregatesfrom quarry operations, gravel, dredged aggregates, china clay stent,china clay wastes, natural stone, recycled bituminous pavements,recycled concrete pavements, reclaimed road base and subbase materials,crushed bricks, construction and demolition wastes, waste/recycled fluegas ashes, crushed glass, slate waste, waste plastics, egg shells, seashells, and mixtures thereof. In one embodiment, the aggregate iscrushed recycled concrete. The crushed recycled concrete can be made bycrushing, grinding, pulverizing, etc. any concrete material includingconcrete compositions that include sand as an aggregate, or morepreferably concrete material from the present disclosure (i.e. cement,aggregate which does not include sand, water, crumb rubber).

In one embodiment, no aggregate, filler, or additive which comprises agroup 13 element is present in the masonry block. In one embodiment, thegroup 13 element is boron. Examples of aggregates, fillers, or additivesthat contain boron include borosilicates, boric acid, boron carbide,boron-containing fibers, boron containing fabrics, boron containingmesh, boron filaments, borax, boron oxide, ferro boron and boratedstainless steel, colemanite, ulexite, kemite, tincal, boron nitride,borates, or mixtures or boron isotopes thereof.

The crumb rubber-containing masonry blocks of the present disclosure maycontain cement in the range of 5-10 wt %, relative to the total weightof the masonry block. The crumb rubber-containing masonry blocks mayinclude non-rubber aggregate (i.e., which is not crumb rubber) in therange of 75-80 wt % relative to the total weight of the masonry block.The crumb rubber-containing masonry blocks may include water in therange of 5-8 wt % relative to the total weight of the masonry block.

The crumb rubber-containing masonry blocks may include crumb rubber inthe range of 5-10% relative to the total weight of the masonry block.Preferably, the crumb rubber-containing masonry block may have a wt %composition that includes 5-10% cement, 75-80% aggregate, 5-8% water; or5-10% crumb rubber, 5-10% cement, 75-80% aggregate, 5-8% water; or 5-10%crumb rubber, 5-10% cement, 75-80% aggregate, 5-8% water.

In one embodiment, the masonry block has a unit weight of 1000-1250kg/m³, preferably 1020-1200 kg/m³, preferably 1025-1150 kg/m³.Conventional masonry blocks have a unit weight of around 1259-1260kg/m³, therefore, the masonry block of the present disclosure may have aunit weight (in kg/m³) that is 10-20% lower than that of conventionalconcrete blocks, which can cause less weight to be placed on a buildingframe and less wear on any concrete handling machinery.

In one embodiment, the masonry block has a water absorption of 6.0-9.0%,or 6.5-8.98%, or 6.8-8.95%, or 6.9-8.93% as determined by ASTM C 642.

In one embodiment, the masonry block has a thermal conductivity of0.3-0.58 W/m·k, preferably 0.34-0.56 W/m·k, preferably 0.36-0.54 W/m·k,preferably 0.4-0.52 W/m·k. Conventional masonry blocks have a thermalconductivity of 0.585 W/m·k, and therefore the masonry blocks of thepresent disclosure (i.e. containing crumb rubber) have a lower thermalconductivity which may provide energy conservation in buildingsemploying the crumb rubber masonry blocks.

The masonry block may be of many forms, sizes and structures, such as astretcher block, a corner block, a pillar block, a jam lock, a partitionblock, a lintel block, a frogged brick block and a bull nose block. Themasonry block may include shapes and structures conventionally known asconcrete masonry units (CMU). The masonry block unit includes “splitface” masonry block having, at one exposed, a rough surface obtained bysplitting a single unit.

Preferably, the masonry block includes one or more chambers that areopen on at least a top and bottom of the masonry block. When used forpurposes of construction the masonry blocks are laid one atop another ina staggered array to form connected vertical chambers.

Such chambers may accommodate one or more reinforcing structures such asreinforcing steel (“rebar”). The vertical chambers may also be filledwith one or more insulation materials, such as spray-in foam to reducethe thermal conductivity of the structure that is constructed from themasonry blocks.

The masonry blocks generally have a rectangular structure with top andbottom surfaces representing bonding services onto which a curableadhesive such as a mortar is applied when the masonry blocks arestacked. At least two external face surfaces form the surfaces of wallsand/or provide a substrate onto which a further finish such as a paint,plaster or mortar may be applied. Typically, the ends of the masonryblock include indentations, protrusions or cavities which permit matingand matching of neighboring blocks during construction. Theseindentations, protrusions and/or cavities may be present on top surfacesand faces of the masonry blocks to permit end-to-end mating ortop-to-bottom mating between neighboring masonry blocks. In largermasonry blocks, a plurality of chambers may be present with each chamberseparated from one another by an interconnecting web that connects frontand back faces of the masonry block. The web functions to improve thestrength of the masonry blocks and improve bonding between blocks whenassembled in a stack configuration. In other embodiments the masonryblocks are solid and have no major cavity. In this form the masonryblocks may be used as bricks, papers or other architectural constructionunits useful for providing a reinforced or strengthened service.

FIG. 3 shows a masonry block (1-1) in the form of a conventionalstructure block. Front and back exposed faces (1-2) and (1-3) and endfaces (1-4) and (1-5) form a face perimeter of the masonry block. A topsurface (1-6) is the bonding surface of the vertically stacked masonryblock. Cavities (1-7) are present within the masonry block and areseparated by a web (1-8). End face (1-4) shows indentations that maymatch and mate with protrusions of a neighboring masonry block when setin place.

The dimensions of the masonry blocks may vary (FIGS. 5A-5D). A typicalstructure of a masonry block has a configuration in which the length ofthe exposed face ranges from 10 cm to 1 m, preferably 20-80 cm,preferably 40-60 cm. When in the shape of a rectangle, the masonry blocktypically has a thickness that is less than the length, preferably thethickness is 5-80 cm, preferably 10-60 cm, preferably 20-40 cm. Theheight of the masonry block is typically more similar to the thicknessof the masonry block and ranges from 5-80 cm, preferably 10-60 cm, or20-40 cm. In other embodiments, the masonry block is square in which thethickness of the masonry block is substantially the same as its length.The height may vary in square masonry blocks but may alternately be thesame as the thickness or length.

In other embodiments, the masonry block is solid (FIG. 4A).and has nochamber or empty core. FIG. 3 describes a masonry block structure thatis solid and has dimensions similar to the dimensions of a masonry blockdescribed above. In other embodiments the solid masonry block may haveone or more textured or featured surfaces (FIG. 4B).

FIG. 5A shows the masonry block with two chambers and a single web. FIG.5B describes a masonry block that includes one scored end face to permitinsertion of a reinforcing bar and/or to mate with a protrusion in theend face of a neighboring masonry block. FIG. 5C describes a masonryblock having a relatively low height. FIG. 5D describes a masonry blockhaving a relatively narrow thickness.

In another embodiment of the invention, the crumb rubber is presentwithin the masonry block in one or more sections or portions at a highercontent than the average content of the crumb rubber over the entiremasonry block. For example, a higher crumb rubber content may be presentat or near the faces, edges or within certain domains of the masonryblock. Biasing the crumb rubber content at a face of the masonry blockthat represents the main exposed surface of the masonry block provides aconstruction material that is effective for sound or impact deadening.The crumb rubber content at a face may be, for example, from 20-50% byweight, preferably 30-40% weight percent with weight % determined by thetotal weight of the section or portion of the masonry block thatcontains the crumb rubber. Preferably, such sections are the onlyportions of the masonry block that contain crumb rubber. A section orportion, e.g., one representing a face of the masonry block, canrepresent a face depth of the masonry block of 5 mm, 10 mm, 2 cm, 3 cm,5 cm or 10 cm where such portion represents 5%, 10%, 20%, 30%, 40% or50% of the total face-to-face thickness of the masonry block. Thus, theface of the masonry block may represent a section or portion that isintegral with the masonry block but represents a minor portion of thetotal volume or total weight of the masonry block. Preferably, only asingle face of the masonry block contains a biased amount of crumbrubber. In other embodiments, more than one face or portion of themasonry block contains an increased quantity of the crumb rubber.

In another embodiment of the invention, the crumb rubber is contained ina portion of the masonry block that is located mainly internal to themasonry block with only a small exposure at any face thereof. In thisway, a section or layer of the masonry block that contains a relativelyhigher quantity of crumb rubber than the content of crumb rubber in themasonry brick overall, is buried within the masonry block and crumbrubber is exposed in any face of the masonry block only to the extentthat edge portions of the layer may be exposed on a face. Inclusion ofthe crumb rubber in an internal layer provides advantages relating tothe physical properties of the masonry block. Properties, such asthermal mass, thermal conductivity, and impact resistance all may all beimproved by the inclusion of a crumb rubber-containing layer or sectionwithin the masonry block structure.

Masonry blocks containing crumb rubber-enhanced sections or portions maybe made by selectively sequentially pouring different concretecompositions into a masonry block mold. Pouring a crumbrubber-containing concrete as the first and last layer of the masonryblock forms a masonry block in which both outside exposed faces have anincreased content of crumb rubber in comparison to the overall crumbrubber content of the masonry block.

Likewise, pouring a layer of a crumb rubber-containing concrete into themold as an intermediate layer, forms a masonry block in which the crumbrubber-containing later is located internally or buried within themasonry block structure.

One embodiment includes a masonry block comprising crumb rubber,aggregate, cement, and water. In one embodiment, crumb rubber, cement,and aggregate are placed in a concrete mixer and dry mixed for a timeperiod in the range of 30 seconds-10 minutes, 45 seconds-8 minutes, or50 seconds-5 minutes. Preferably, the crumb rubber, cement, andaggregate are dry mixed for 1 minute. Mixing the crumb rubber, cement,and aggregate forms a mixture in which the crumb rubber is homogenouslydispersed. Following the dry mixing process, water is added to themixture of crumb rubber, cement, and aggregate. The water is slowlypoured into a mixer while the mixer turns the cement, crumb rubber, andaggregate for a time period in the range of 1-10 minutes, 2-8 minutes,or 3-6 minutes.

Preferably, the water is mixed into the mixture for a time period of 3minutes.

The mixture of water, crumb rubber, cement, and aggregate is fed into asteel mold to create a masonry block shape. The fresh mix is compactedin the mold by using a steel rod. After setting into the mold, themixture is air cured for a time period in the range of 1-10 hours, 2-8hours, or 4-7 hours. Preferably, the mixture is air cured in the moldfor a time period of 6 hours and then removed from the mold, whichresults in a masonry block. The masonry block is then cured for a timeperiod of 15-30 days in a cure tank filled with lime-saturated water ata temperature in the range of 20-30° C., 21-29° C. or 22-28° C.Preferably, the masonry block sample is cured for a time period of 28days in a cure tank filled with lime-saturated water at a temperature of22′C.

In one embodiment, the crumb rubber is a thermoset or thermoplasticpolymer in the form of recycled crumb rubber from automotive and truckscrap tires.

In another embodiment, the CR augmented masonry blocks do not requirenew processing routes as the same route used for producing conventionalblocks can be adopted.

In another embodiment, the CR augmented masonry blocks satisfy thestandard for utilization in the construction industry.

Masonry blocks may be formed from similar quantities of crumb rubber incombination with significant quantities of limestone powder. Forexample, the cementitious composition containing 15% crumb rubber byweight and 50% LSP by weight provides a compressive strength of 6.9 MPameeting ASTM standards for masonry blocks. Excellent compressivestrength is obtained even for cementitious compositions containing 15 wt% rubber and 25% LSP with an ideal crumb rubber content of 15-20% and anLSP content of about 25%. Such cementitious compositions aresubstantially economically advantaged in comparison to conventionalrubber-containing cementitious compositions which contain substantiallygreater amounts of a cement such as Portland cement which must beobtained as a purchased material.

The examples below are intended to further illustrate the masonryblocks, their characterization, and uses thereof, and are not intendedto limit the scope of the claims.

EXAMPLES

A comparative analysis was carried out between conventional cementitiouscomposites and corresponding cured composites, and cementitiouscomposites containing CR and corresponding cured composites. Theinventive CR-containing cementitious composites are able to form curedcomposites in the form of CR-containing masonry blocks having acombination of properties that satisfy the ASTM non-load bearingrequirements, such as compressive strength in addition to satisfying thewater absorption requirements.

Conventional masonry blocks are composed of aggregate, cement, water andsand. In the present disclosure, sand is replaced at least in part(preferably in a major amount) with crumb rubber. The inventive crumbrubber masonry block was evaluated for the performance in conditionssimilar to the ones faced in the construction industry. The conventionalmasonry blocks are composed of the following ingredients with the listedpercentages as listed in Table 1:

TABLE 1 Percent Composition of Conventional Masonry Blocks IngredientComposition Cement 25% Aggregate 55% Water  5% Sand 15%

FIG. 1 depicts conventional masonry blocks that have an average weightof 20.150 kg. Table 2 describes inventive and comparative cementitiouscomposites in the form of cured masonry blocks.

TABLE 2 Composition of Crumb-Rubber Containing Masonry Blocks ExampleNo. 5 6 7 8 9 2 3 4 15% 20% 25% 15% 20% Mixture 15% 20% 25% rubber,rubber, rubber, rubber, rubber, composition rubber rubber rubber 25% LSP25% LSP 25% LSP 50% LSP 50% LSP Cement (gm) 215 215 215 154 154 154 102102 LSP (gm) — — — 51 51 51 102 102 CKD (gm) — — — — — — — — Water (gm)123 142 142 127 132 136 137 147 Agg # 4 (gm) 903 882 862 859 838 819 855835 Agg # 8 (gm) 270 264 257 256 250 245 255 249 Sand (gm) 665 611 560632 581 532 629 578 Rubber #3 (gm) 47 61 75 45 58 71 44 58 Rubber #2(gm) 47 61 75 45 58 71 44 58 Rubber #1 (gm) 23 31 37 22 29 35 22 29 SP(ml) 3 3 3 2 2 2 2 2 Unit Weight (kg/m³) 2100 1975 2055 2074 2024 19562071 2081 Compressive 10.1 8.9 7.9 9.6 8.3 4.2 6.9 6 strength (MPa)Example No. 10 11 12 13 14 15 16 25% 15% 20% 25% 15% 20% 25% Mixturerubber, rubber, rubber, rubber, rubber, rubber, rubber, composition 50%LSP 25% CKD 25% CKD 25% CKD 50% CKD 50% CKD 50% CKD Cement (gm) 102 154154 154 102 102 102 LSP (gm) 102 — — — — — — CKD (gm) — 51 51 51 102 102102 Water (gm) 156 137 137 146 147 157 156 Agg # 4 (gm) 815 857 837 817851 831 812 Agg # 8 (gm) 244 256 250 244 254 248 243 Sand (gm) 530 630579 531 626 576 527 Rubber #3 (gm) 71 45 58 71 44 58 70 Rubber #2 (gm)71 45 58 71 44 58 70 Rubber #1 (gm) 35 22 29 35 22 29 35 SP (ml) 2 2 2 22 2 2 Unit Weight (kg/m³) 2050 2102 1992 2001 2078 2011 1950 Compressive4.3 7.4 5.5 5.3 5.4 4.2 4.2 strength (MPa)

FIG. 2 shows a masonry block fabricated with a CR-containingcementitious composite and which weighs on average 17.6 kg.

The table below describes a family of cementitious compositions cured inthe form of masonry blocks and that contain one or more of CKD orlimestone powder. Comparative cured cementitious compositions aredescribed in which CKD and/or limestone powder is absent. Each of thecured compositions contains crumb rubber particles. As a baseline,several compositions are described that do not contain limestone powder(LSP) or CKD.

The masonry blocks obtained from curing the cementitious composition ina mold have compressive strengths ranging from 10.1 to 7.9 MPa testedaccording to ASTM C 39. Masonry blocks formed from cementitiouscompositions containing 15% crumb rubber and 25% CKD are shown toprovide a compressive strength of 7.4. Such masonry blocks which containsignificant amounts of industrial by-product or waste are of a specialinterest to building material.

As is shown by at least Examples 5, 6, 8 and 11, masonry blocks havingdesirable compressive strength can be formed from cementitiouscompositions containing significant amounts of industrial by-productsand waste, such as crumb rubber, limestone powder and/or cement kilndust.

It can be seen from the conducted tests that CR-containing masonryblocks meet the requirement ASTM requirements for strength of non-loadbearing blocks and exhibited reasonable improvement in thermalcharacteristics. The addition of different percentages and types ofcrumb rubber proved to alter the properties of the developed blocks.

1. A masonry block with a cavity web, comprising: 5-10 wt % cement;75-80 wt % of an aggregate, which is not crumb rubber; 5-8 wt % water;5-10 wt % crumb rubber relative to the total weight of the masonryblock; wherein the crumb rubber is in the form of coarse particleshaving a particle size of 1.5-5 mm, fine particles having a particlesize of 50-250 μm, or a mixture of the coarse particles and the fineparticles; and at least one of cement kiln dust and limestone powder,wherein the limestone powder has an average particle size of from 1 to50 μm, wherein the aggregate is at least one selected from the groupconsisting of a crushed recycled concrete material and crushed limestonehaving an average particle size of greater than 1 millimeter, andwherein the masonry block has a rectangular form with a front face, aback face, a first end face and a second end face forming a faceperimeter surrounding a plurality of interior cavities separated by aweb.
 2. The masonry block of claim 1, wherein the crumb rubber is in theform of coarse particles having a particle size of 1.5-5 mm.
 3. Themasonry block of claim 1, wherein the crumb rubber is in the form offine particles having a particle size of 50-250 μm.
 4. The masonry blockof claim 3, wherein the fine particles have a particle size of 100-148μm.
 5. The masonry block of claim 1, wherein the mixture of the coarseparticles and fine particles is present.
 6. The masonry block of claim5, wherein a ratio of the coarse particles to the fine particles rangesfrom 2:1 to 1:2.
 7. The masonry block of claim 6, wherein the ratio ofthe coarse particles to the fine particles is about 1:1.
 8. The masonryblock of claim 1, which has a unit weight of 1000-1250 kg/m³.
 9. Themasonry block of claim 1, wherein the masonry block has a waterabsorption of 6.0-9.0% as determined by ASTM C
 642. 10. (canceled) 11.The masonry block of claim 1, wherein no aggregate, filler, or additivewhich comprises a group 13 element is present in the masonry block. 12.The masonry block of claim 11, wherein the group 13 element is boron.13. The masonry block of claim 1, wherein the crumb rubber is carboxylicacid surface modified crumb rubber obtained by treating crumb rubberwith hydrogen peroxide.
 14. The masonry block of claim 1, which has a wt% of crumb rubber ranging from 12 to 18%, relative to the total weightof the masonry block.
 15. The masonry block of claim 1, which consistsof the cement, the aggregate, the water, the crumb rubber, the limestonepowder and the cement kiln dust.